Method of foaming a polymer composition using zeolite and foamed articles so made

Abstract

The present invention relates to a method of foaming a polymer comprising the steps of providing a composition comprising said polymer and a zeolite in an amount of 0.3% or more based on the weight of said polymer and extruding said composition. The invention further relates to foamed articles and to the use of zeolites as foaming agents in the foaming of polymers.

What is claimed is:  
     
       1. Foamed article comprising a foamed fluoropolymer comprising a zeolite in amount of at least 0.3% by weight based on the weight of the foamed polymer. 
     
     
       2. Foamed article according to  claim 1  wherein said foamed article is selected from a film, a cable having said foamed layer thereon, a tube and a piezoelectric substrate. 
     
     
       3. Foamed article according to  claim 1  wherein said zeolite is present in an amount of at least 0.5% by weight based on the weight of polymer. 
     
     
       4. Foamed article according to  claim 1  wherein said zeolite has an average particle size of not more than 15 μm. 
     
     
       5. Foamed article according to  claim 1  wherein said zeolite has a water content of less than 10% by weight. 
     
     
       6. Foamed article according to  claim 1  wherein said foamed layer of polymer comprises foam cells having an average size of not more than 100 μm. 
     
     
       7. Foamed article according to  claim 1  wherein said fluoropolymer is a melt processable fluoropolymer. 
     
     
       8. Foamed article according to  claim 7  wherein said melt processable fluoropolymer is a fluoropolymer comprising one or more units derived from fluorinated monomers selected from the group consisting of tetrafluoroethylene, vinylidene fluoride, vinyl fluoride, chlorotrifluoroethylene, fluorinated alkyl olefins, fluorinated vinyl ethers and fluorinated allyl ethers and optionally one or more units derived from non-fluorinated olefins. 
     
     
       9. Foamed article according to  claim 1  wherein said zeolite is selected from the group consisting of zeolite Y, zeolite X, zeolite A, zeolite ZSM-5 and zeolite beta. 
     
     
       10. Method of foaming a fluoropolymer comprising the steps of providing a composition comprising said fluoropolymer and a zeolite in an amount of 0.3% or more based on the weight of said fluoropolymer and thermally processing said composition to form a foamed fluoropolymer. 
     
     
       11. Method according to  claim 10  wherein said zeolite is present in an amount of at least 0.5% by weight based on the weight of polymer. 
     
     
       12. Method according to  claim 10  wherein said zeolite has an average particle size of not more than 15 μm. 
     
     
       13. Method according to  claim 10  wherein said zeolite has a water content of not more than 10% by weight. 
     
     
       14. Method according to  claim 10  wherein said fluoropolymer is a melt processable fluoropolymer. 
     
     
       15. Method according to  claim 14  wherein said fluoropolymer is a fluoropolymer comprising one or more units derived from fluorinated monomers selected from the group consisting of tetrafluoroethylene, vinylidene fluoride, vinyl fluoride, chlorotrifluoroethylene, fluorinated alkyl olefins, fluorinated vinyl ethers and fluorinated allyl ethers and optionally one or more units derived from non-fluorinated olefins. 
     
     
       16. Method according to  claim 10  wherein said zeolite is selected from the group consisting of zeolite Y, zeolite X, zeolite A, zeolite ZSM-5 and zeolite beta. 
     
     
       17. Method according to  claim 10  wherein said composition is foamed in the absence of a physical foaming agent. 
     
     
       18. Method according to  claim 10  wherein there is further added to said composition a physical foaming agent. 
     
     
       19. Method of utilizing a zeolite as a foaming agent to cause the foaming of a polymer. 
     
     
       20. Method according to  claim 19  wherein said polymer is a fluoropolymer.